This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The high frequency of pre-existing immunity to the Ad5 vector has been shown to suppress the immunogenicity and possibly impair the safety of rAd5 vaccines for HIV-1. To overcome this hurdle, we have developed novel replication-incompetent rAd vector-based vaccines derived from rare Ad serotypes and chimeric viruses.